Hunger is one of our most basic and primitive drives. When we are deprived of food, for whatever reason, we become intensely focused on satiating that craving. We want calories, and we want them now. Everything else--including time and money--is merely an aid for finding and acquiring rich, caloric food.
This makes sense. It's survival. Yet beyond this fundamental drive for satiety and nutrition, surprisingly little is known about hunger's influence on our behavior.